Scanning electron microscopic study of the muscle fiber arrangement in the rat cricopharyngeal muscle

Neuromuscular Specializations of the Human Hypopharyngeal Muscles

The hypopharyngeal muscles in humans play a vital role in swallowing, speech, and respiration. Increasing evidence indicates that these muscles are specialized to perform life-sustaining upper aerodigestive functions. This review aims to provide current knowledge regarding the key structural, physiological, and biochemical features of the hypopharyngeal muscles, including innervation, contractile properties, histochemistry, biochemical properties, myosin heavy chain (MyHC) expression and regulation, and age-related alterations. These would clarify the unique neuromuscular specializations of the human hypopharyngeal muscles for a better understanding of the functions and pathological conditions of the pharynx and for the development of novel therapies to treat related upper airway disorders.

A complex muscle fiber network in the cricothyroid muscle: a scanning electron microscopic study

OBJECTIVES

To examine the three-dimensional ultrastructure of cricothyroid (CT) muscle fibers to elucidate their morphologic characteristics with regard to the specific functions of the muscle.

STUDY DESIGN

An anatomic animal study.

METHODS

The CT muscles of five adult rats were processed using the HCl-hydrolysis method to remove the peri- and intramuscular connective tissue components. The fine muscle fiber arrangements were observed by scanning electron microscopy.

RESULTS

Complex muscle fiber interconnections (myomyous junctions) were identified in the muscles. Myomyous junctions were characterized by the connection of many villous processes that were 1 to 2 mum in diameter and 2 to 4 mum in length with a serrated appearance at the ends of a lateral branch or a bifurcating trunk of the muscle fibers.

CONCLUSIONS

Myomyous junctions form a complex muscle fiber network, which is thought to synchronize the activity of the CT muscle fibers. This is the first three-dimensional demonstration of the muscle fiber network in the CT muscle; this network may play a major role in the functional specificity of the CT muscle.